1. Field of the Invention
This invention relates to a fan located between an internal combustion engine and a radiator and rotatingly driven from a rotational shaft of the engine.
2. Description of the Prior Art
In a liquid cooled internal combustion engine, a cooling liquid is circulated through jackets in the cylinder block and cylinder head of the engine and, after being led out of the internal combustion engine, passed through a radiator to exchange heat with air flows from a fan which is provided in association with pipes and fins of the radiator. After being cooled, the liquid is recirculated to the jackets of the internal combustion engine. Normally, the cooling fan is rotatingly driven from a rotational shaft of the engine. With regard to the relation between the fan and radiator, it is the usual practice to provide an axial flow type fan which has its rotational face located close to the radiator and is driven by a rotational shaft which is positioned parallel with the air passages in the radiator. Namely, the fan is in most cases located between a radiator and an internal combustion engine, positioning the radiator on the suction (upstream) side of the fan in consideration of the cooling effects on the radiator of the air flows produced by the axial flow type cooling fan.
With such an arrangement, the internal combustion engine is located in a position close to the discharge (downstream) side of the cooling fan, so that the air flows which are formed by the fan impinge upon the internal combustion engine, producing a back pressure which reduces the air flow to be generated by the cooling fan. Such a reduction of air flow is generally prevented by forming behind the radiator a shroud which has an inner diameter slightly larger than the diameter of the fan, regulating the air flows uniform on the suction (upstream) side of the fan by rotating same at the rear edge portion of the shroud. In this case, however, the air flows on the discharge (downstream) side of the fan diverge radially outward upon impingement on the engine which constitutes a resisting body, forming reverse flows at the end portions of the fan blades as indicated by arrows of chain line A in FIG. 1. These reverse air flows form vortices around the end portions of the fan blades within the shroud, further lowering the air flow rate.